1. Field of the Invention
The present invention relates to a PLL circuit.
2. Description of the Prior Art
Conventionally, a PLL (Phase Locked Loop) circuit has been known (refer to a Patent Document 1, for example). A reference frequency signal is input to the PLL circuit. When the reference frequency signal is no longer input to the PLL circuit, a current continues to flow to a charge pump circuit disposed between a loop filter and a phase comparator of the PLL circuit from the loop filter of the PLL circuit. As a result, an operational amplifier constructing the loop filter saturates.
(Patent Document 1) Japanese Laid-Open Patent Publication (Kokai) No. 2000-40959